Electronic systems, such as computers typically include a protective case, one or more circuit boards mounted inside the case, and one or more components such as a processor or a power supply mounted to each of the boards. In operation, the components generate heat that the system must remove from the case to prevent overheating and the damage it may cause.
To remove the heat, the system typically includes one or more fans that draw cool air into the case, circulate the drawn air within the case such that it absorbs the heat generated by the components, and expel the heated air from the case. The rate at which the heat is removed is typically proportional to the rate at which the air flows into and out of the case. The greater the flow rate, the greater the heat-removal rate and vice versa.
To prevent hot spots within the case, however, the system designer typically must consider the size, location, and orientation of the boards and components when designing the cooling system. The boards and components add resistance to the airflow paths within the case. Because the air will follow the paths of least resistance, components that lie along high-resistance paths may overheat if the cooling system is not designed to provide adequate flow rates along these high-resistance paths. Therefore, the designer analyzes the layout of the boards and components and determines the size, speed, and placement of the cooling fans that will provide adequate flow rates along all of the airflow paths for the lowest cost. Factors that affect the cost of the cooling system include the number of fans, the amount of power they consume, and how difficult it is to manufacture/install the cooling system.
Furthermore, to keep electromagnetic interference (EMI) to an acceptable level, the designer typically must consider the layout of the boards and components within the case when designating an EMI shielding system.
To take advantage of the economies of scale in mass production, most models of a system include the same cooling and shielding systems, but may include different circuit boards or components. For example, a high-end model of a data server may include a mother board with four processors mounted thereto, while a low-end model of the same server might include the same board with only one processor mounted thereto. To ensure that a system that includes all of the possible boards and components is properly cooled and shielded the cooling and shielding systems are typically designed for such a fully populated system. Consequently, when one or more of the components or boards are omitted from the system, the airflow and EMI footprint of the system may change such that the cooling system, shielding system, or both are no longer adequate.
FIGS. 1 and 2 illustrate the effect that an omitted component can have on the air flow within an electronic system.
FIG. 1 illustrates an electronic system 20 that includes components 22 and 24 attached to the circuit boards 26, 28 and 30. Air flows along paths 32, 34 and 36 between the circuit boards 26, 28 and 30 to remove heat from the components 22 and 24. Because the cooling system (not shown in FIGS. 1 and 2) is designed for the fully populated system 20, the air flow adequately cools the components 22 and 24.
But, as FIG. 2 illustrates, when the component 24 is removed from the circuit board 28, the air flowing along the path 34 does not encounter the resistance of the omitted component 24. Consequently, assuming the same overall air flow into the case as in FIG. 1, air flow along the path 34 increases and the air flow along the paths 32 and 36 decreases. Consequently, the components 22 on the boards 26 and 30 may overheat. One solution is to increase the overall air flow (e.g. by increasing the fan speed) to a level where the flow along the paths 32 and 34 is sufficient to cool the components 22 on the boards 26 and 30. However, this often increases the amount of power consumed by the cooling system and may reduce the life of the cooling fans. It also may increase costs if a technician has to manually adjust the fan speed of each partially populated system.
Still referring to FIGS. 1 and 2, the omission of the component 24 from a circuit board of an electronics system can change the EMI footprint in a similar manner, and tailoring the EMI shielding for each different system can be prohibitively expensive.
In one aspect of the invention, a fluid-flow balancer for taking the place of a system component having an air-flow resistance includes a flow-resistance element and a mount. The flow-resistance element is operable to mimic the air-flow resistance of the component, and the mount is operable to mount the flow-resistance member within the system.
By mimicking the air-flow resistance of an omitted component, such a balancer can maintain the flow along the air paths within a system at proper levels without tweaking or redesigning the cooling system. In a related aspect of the invention, the balancer also mimics the EMI suppression provided by the omitted component.